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Commit 4c8fbca5 authored by Sam Ravnborg's avatar Sam Ravnborg
Browse files

kbuild: whitelist false section mismatch warnings 



In several cases the section mismatch check triggered false warnings.
Following patch introduce a whitelist to 'false positives' are not warned of.
Two types of patterns are recognised:
1) Typical case when a module parameter is _initdata
2) When a function pointer is assigned to a driver structure

In both patterns we rely on the actual name of the variable assigned

Signed-off-by: default avatarSam Ravnborg <sam@ravnborg.org>
parent cc006288

scripts/mod/modpost.c

+89 −0
Original line number Diff line number Diff line
@@ -451,6 +451,89 @@ static char *get_modinfo(void *modinfo, unsigned long modinfo_len, 
	return NULL;

}



/**

 * Test if string s ends in string sub

 * return 0 if match

 **/

static int strrcmp(const char *s, const char *sub)

{

        int slen, sublen;

	

	if (!s || !sub)

		return 1;

	

	slen = strlen(s);

        sublen = strlen(sub);

	

	if ((slen == 0) || (sublen == 0))

		return 1;



        if (sublen > slen)

                return 1;



        return memcmp(s + slen - sublen, sub, sublen);

}



/**

 * Whitelist to allow certain references to pass with no warning.

 * Pattern 1:

 *   If a module parameter is declared __initdata and permissions=0

 *   then this is legal despite the warning generated.

 *   We cannot see value of permissions here, so just ignore

 *   this pattern.

 *   The pattern is identified by:

 *   tosec   = .init.data

 *   fromsec = .data

 *   atsym   =__param*

 *   

 * Pattern 2:

 *   Many drivers utilise a *_driver container with references to

 *   add, remove, probe functions etc.

 *   These functions may often be marked __init and we do not want to

 *   warn here.

 *   the pattern is identified by:

 *   tosec   = .init.text | .exit.text

 *   fromsec = .data

 *   atsym = *_driver, *_ops, *_probe, *probe_one

 **/

static int secref_whitelist(const char *tosec, const char *fromsec,

			  const char *atsym)

{

	int f1 = 1, f2 = 1;

	const char **s;

	const char *pat2sym[] = {

		"_driver",

		"_ops",

		"_probe",

		"_probe_one",

		NULL

	};

	

	/* Check for pattern 1 */

	if (strcmp(tosec, ".init.data") != 0)

		f1 = 0;

	if (strcmp(fromsec, ".data") != 0)

		f1 = 0;

	if (strncmp(atsym, "__param", strlen("__param")) != 0)

		f1 = 0;



	if (f1)

		return f1;



	/* Check for pattern 2 */

	if ((strcmp(tosec, ".init.text") != 0) && 

	    (strcmp(tosec, ".exit.text") != 0))

		f2 = 0;

	if (strcmp(fromsec, ".data") != 0)

		f2 = 0;



	for (s = pat2sym; *s; s++)

		if (strrcmp(atsym, *s) == 0)

			f1 = 1;



	return f1 && f2;

}



/**

 * Find symbol based on relocation record info.

 * In some cases the symbol supplied is a valid symbol so
@@ -518,6 +601,7 @@ static void find_symbols_between(struct elf_info *elf, Elf_Addr addr, 
/**

 * Print a warning about a section mismatch.

 * Try to find symbols near it so user can find it.

 * Check whitelist before warning - it may be a false positive.

 **/

static void warn_sec_mismatch(const char *modname, const char *fromsec,

			      struct elf_info *elf, Elf_Sym *sym, Elf_Rela r)
@@ -537,6 +621,11 @@ static void warn_sec_mismatch(const char *modname, const char *fromsec, 
	if (refsym && strlen(elf->strtab + refsym->st_name))

		refsymname = elf->strtab + refsym->st_name;



	/* check whitelist - we may ignore it */

	if (before && 

	    secref_whitelist(secname, fromsec, elf->strtab + before->st_name))

		return;

	

	if (before && after) {

		warn("%s - Section mismatch: reference to %s:%s from %s "

		     "between '%s' (at offset 0x%llx) and '%s'\n",